This is something I’ve wondered for a long time and I figured it would be a really great place to start: Does taking a bath consume more water than taking a shower?
How I will do this
First, I measured my tub to to see how much water I used during an average bath (See image below). My bath is slanted and because I am not a mathematician, I was unable to find a formula to get the precise quantity of water. Turns out I used between 29-38 gallons of water.
Second, I measured the water flow of my current shower head. I let the water run for 30 seconds and measured that amount of water in liters. I multiplied that amount by two to get the LPM (liters per minute) value and used a conversion calculator from google to get the GPM (gallons per minute).
My manual measurement for my shower head flow rate at 2.5 GPM was quite accurate. Although when I bought the shower head, I wasn’t thinking about the flow rate, when I looked at the model online (since I threw away the box), I saw it indeed have a flow rate of 2.5GPM or 9.5 LPM.
Table 1:
My estimates of water consumption from my bath/shower
| Measurement | GPM | LPM | Total volume (G) | Total volume (L) |
| Initial measurement of the volume of water in my bathtub | 29.77 – 38.3 | 112.7 – 145 | ||
| Rate of shower | 2.5 | 9.5 | 25 – 37.5 (for 10-15 minutes) | 95 – 142.5 (for 10-15 minutes ) |
| Rate of tub tap | 4.75 | 18 |
To visually represent my experiment, see the graph below. In T#, the # represents the number of minutes I let the tap run for my bath before shutting off the water. If I take a 15 minute shower, I am using as much water as if I was taking a bath with 38 gallons (the upper limit of my estimation).
Graph 1:
My Shower versus Bath water use
RESEARCH
Next I wanted to compare my personal water consumption with the information available online. What is the internet saying about this debate?
Bath Water consumption
I used many references and made a list of 3 different sizes of baths. There seemed to be a general consensus with baths using about
- Lowest: 31.3 gallons or 118.4 liters per bath
- Middle: 36 gallons or 136.3 liters per bath
- Highest: 48.5 gallons or 183.6 liters per bath
We need to consider the argument that taking a bath doesn’t clean as well as taking a shower. Some people may not bathe to clean and take a shower after bathing. That means that 100% of the water used in the bath was wasted (or I guess used for relaxation purposes only).
Shower water consumption
There was also a general consensus that taking showers consumed less water than taking a bath, using about
- Lowest: 12.6 gallons or 47.7 liters per shower
- 1.4 gallons/min or 5.3 liters/min (low flow shower head)
- Middle: 23.5 gallons or 89.1 liters per shower
- 2.4 gallons/min or 9 liters per minute (standard shower head)
- Highest: 40.9 gallons or 154.8 liters per shower
- 5.1 gallons per minute or 19.4 liters per minute (old shower heads)
However, most of these were estimated with very short shower times between 5 and 10 minutes (average around 8 minutes). This is probably not representative of the time most people spend in the shower. Furthermore, this was per shower, not reflecting the many people (some I know personally) who take more than one shower per day.
Bath versus Shower water consumption
I plotted a graph to see how long a shower you could take with each type of shower head before you would pass the amount of water used to take a bath (See table 2 and graph 2).
Table 2:
Time (in minutes) to use as much water in a shower as in a bath
| Low flow shower head | Average shower head | Old Shower head | |
| Small bath (31.3) | 22 | 13 | 6 |
| Average bath (36) | 26 | 15 | 7 |
| Big bath (48.5) | 35 | 20 | 10 |
- With a low flow shower head, you could take a 22 minute shower before reaching the amount of water used in the most water efficient bath.
- With a regular shower head, by 13 minutes you have already passed the level of water used in the most efficient bath and by 15 minutes you’ve used the amount of water used in an average bath.
- Using an old shower head is by far the worst for water consumption, taking only 10 minutes to use as much water as a big bath.
Graph 2:
Bath versus shower water consumption
Discussion
In general, showers do consume less water than taking a shower. However, there are several things that could alter the results including:
- Length of the shower
- Flow of shower head
- Amount of water used in bath
- Number of showers per day
Conclusion
This experiment has been honestly eye opening for me. I always knew my showers were too long and in the past I have tried many things to decrease them, but with this I can see first hand how my shower habits are consuming an insane amount of water. I also see more visually that my 20 minute showers are consuming more than an average bath, so if all I feel like doing is soaking in the water, I should really draw a bath instead. I can easily say that I am sufficiently motivated to change my habits and will try once more in the coming months.
Let me know what you think about my experiment and research!